The present invention relates to an apparatus and method for continuously vulcanizing endless rubber belts such as flat belts or V-belts, and more specifically, the present invention relates to a vulcanizing apparatus and method particularly suited to vulcanization of toothed belts or the like.
Among vulcanizing apparatus of this nature, there is one type called "rotary cure" having the following construction: As shown in FIG. 9, an endless unvulcanized rubber belt molding A is placed across a vulcanizing drum 32 and a tension pulley 30, which are arranged at a certain distance from each other. An endless pressurizing band 41 is placed around a pair of guide rolls 33 and arranged with the vulcanizing drum 32 between and also around a tension roll 35 which is arranged in an intermediate axis between the guide rolls 33. A tensile force is exerted to the tension roll 35 by means of a pressure cylinder 39, and the pressurizing band 41 is pressed against the outside of the rubber belt molding A on the circumference of the vulcanizing drum 32 to pressurize the molding A. The vulcanizing drum 32 is rotated, while the circumferential surface of the vulcanizing drum 32 is heated by an internal heat source. The prior art literature includes provisional Patent Publication SHO-59-68222 in which a vulcanization apparatus having a construction similar to that of FIG. 9 is described.
The above-mentioned vulcanizing apparatus of the rotary cure type (FIG. 9), however, has some problems that will be explained later. Hence endless rubber belts are normally vulcanized by the following vulcanizing method using a vulcanizing apparatus as shown in FIG. 10: Rubber belt materials comprising, for example, unvulcanized rubber sheets, cords and canvas, are wound and molded over the outer circumferential surface of a cylindrical vulcanizing drum 50. Then a rubber sleeve 51 is placed over the rubber belt molding A. The vulcanizing drum 50 is then lifted by a crane (not illustrated) or the like and placed in a vulcanizing can 52. A cover 52a is closed, and then steam is introduced into the vulcanizing can 52 to pressurize and heat the molding A to vulcanize it.
The aforementioned rotary cure type vulcanizing apparatus (shown in FIG. 9) has the following problems:
(1) The job is complicated and takes much time since an endless rubber belt molding A must be placed across the vulcanizing drum 32 and the tension pulley 30 while both are axially supported. PA1 (2) The pressing force from the pressurizing band 41 works on the vulcanizing drum 32 from only one side. Hence the supporting apparatus for axially supporting the vulcanizing drum 32 must be large enough to bear the large axial load. PA1 (3) As clearly shown in FIG. 9, only a limited portion of the unvulcanized rubber belt molding A is pressurized and heated (vulcanized)at a time. It, therefore, takes much time to vulcanize, and the pressurization of the rubber belt molding A tends to be inadequate to completely remove the air, resulting in defects in the product, such as separation between internal constituent members of the rubber belt molding A and generation of pin holes. PA1 (4) Small-sized rubber belt moldings cannot be vulcanized since the endless belt molding A must be placed across two shafts, namely, the vulcanizing drum 32 and the tension pulley 30. PA1 (5) To facilitate the placement and removal of an endless rubber belt molding A, the vulcanizing drum 32 is cantilevered (axial support ) in many cases. If the vulcanizing drum 32 is of the cantilevered type, the vulcanizing drum 32 will be deflected in the axial direction when the drum 32 is pressed in one direction by the pressurizing band 41. Thus the pressurization of the rubber belt molding A will be irregular. PA1 (1) Placement of the vulcanizing drum 50 in the vulcanizing can 52 and removal of the vulcanizing drum 50 from the vulcanizing can 52 are accomplished largely by manual laborers, and are difficult to be automatized. It is also difficult to secure sufficient workers because of the current shortage of labor. PA1 (2) The operation is a batch process since the whole course of vulcanization is done in one vulcanizing can 52. It, therefore, takes much time to vulcanize, and the production efficiency is low.
The conventional vulcanizing method using the vulcanizing apparatus of FIG. 10 has the following problems: